Liquid crystalline medium

ABSTRACT

The invention relates to a liquid crystalline medium characterized by containing one or more compounds of general formula (I) and one or more compounds of formula (II), wherein R&lt;SUP&gt;1&lt;/SUP&gt;, R&lt;SUP&gt;2&lt;/SUP&gt;, R&lt;SUP&gt;3&lt;/SUP&gt;, R&lt;SUP&gt;4 &lt;/SUP&gt;and c have the meanings as cited in Claim No. 1 .

[0001] The present invention relates to a liquid-crystalline medium, inparticular a liquid-crystalline medium based on a mixture of compoundsof negative dielectric anisotropy, to the use thereof as forelectro-optical purposes, and to displays containing this medium, inparticular displays based on the DAP (deformation of aligned phases),ECB (electrically controlled birefringence), CSH (colour superhomeotropic), VA (vertically aligned) or IPS (in plane switching)effect.

[0002] The principle of electrically controlled birefringence, the ECBeffect or DAP (deformation of aligned phases) effect, was described forthe first time in 1971 (M. F. Schieckel and K. Fahrenschon, “Deformationof nematic liquid crystals with vertical orientation in electricalfields”, Appl. Phys. Lett. 19 (1971), 3912). This was followed by papersby J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J.Robert (J. Appl. Phys. 44 (1973), 4869).

[0003] The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers(1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82Digest Techn. Papers (1982), 244) have shown that liquid-crystallinephases must have high values for the ratio of the elastic constantsK₃₃/K₁₁, high values for the optical anisotropy Δn, and values for thedielectric (DC) anisotropy Δε of from about −0.5 to about −5 in order tobe suitable for high-information display elements based on the ECBeffect. Electro-optical display elements based on the ECB effect have,in the switched-off state, a homeotropic or vertical edge alignment,i.e. an alignment substantially perpendicular to the electrode surfaces.

[0004] More recent types of ECB display having a homeotropic edgealignment are those based on the CSH or VA (vertically aligned) effect,where the latter is also known under the terms VAN (vertically alignednematic) and VAC (vertically aligned cholesteric) effect. CSH displaysare known, inter alia, from H. Hirai, Japan Displays 89 Digest, 184(1989), J. F. Clerc et al., Japan Displays 89 Digest, 188 (1989) and J.F. Clerc, SID 91 Digest, 758 (1991). VAN displays have been described,inter alia, in S. Yamauchi et al., SID Digest of Technical Papers, pp.378 ff (1989), and VAC displays have been described in K. A. Crabdall etal., Appl.Phys.Lett. 65, 4 (1994).

[0005] The more recent VA displays, like the ECB displays alreadydisclosed earlier, contain a layer of a liquid-crystalline mediumbetween two transparent electrodes, the liquid-crystal medium having anegative value for the DC anisotropy Δε. The molecules of thisliquid-crystal layer have a homeotropic or tilted homeotropic alignmentin the switched-off state. Owing to the negative DC anisotropy,realignment of the liquid-crystal molecular parallel to the electrodesurfaces takes place in the switched-on state.

[0006] In contrast to conventional ECB displays, in which theliquid-crystal molecules have, in the switched-on state, a parallelalignment with a preferential direction which is uniform over the entireliquid-crystal cell, in VAN and VAC displays this uniform parallelalignment is usually restricted only to small domains within the cell.Disclinations exist between these domains, also known as tilt domains.

[0007] As a consequence of this, VA displays have greater viewing-angleindependence of the contrast and of the grey shades compared withconventional ECB displays. In addition, displays of this type aresimpler to produce since additional treatment of the electrode surfacefor uniform alignment of the molecules in the switched-on state, suchas, for example, by rubbing, is no longer necessary.

[0008] In contrast to VAN displays, the liquid-crystal media in VACdisplays additionally comprise one or more chiral compounds, such as,for example, chiral dopants, which, in the switched-on state, induce ahelical twist of the liquid-molecules in the liquid-crystal layer by anangle of between 0 and 360°. The twist angle in the preferred case isabout 90°.

[0009] For displays having a vertical edge alignment, the use ofcompensators, such as, for example, optically uniaxially negativecompensation films, has also been proposed in order to compensate forundesired light transmission of the display in the switched-off state atan inclined viewing angle.

[0010] In addition, it is possible by means of a special design of theelectrodes to control the preferential direction of the tilt anglewithout additional surface treatment of the electrodes, such as, forexample, by an alignment layer, being necessary. A CSH display of thistype is described, for example, in Yamamoto et al., SID 91 Digest, 762(1991).

[0011] In IPS displays, the electrical signals are generated in such away that the electric fields have a significant component parallel tothe liquid-crystal layer (in-plane switching). International PatentApplication WO 91/10936 discloses a liquid-crystal display of this type.The principles of operating a display of this type are described, forexample, by R. A. Soref in Journal of Applied Physics, Vol. 45, No. 12,pp. 5466-5468 (1974). EP 0 588 568 discloses various ways of addressinga display of this type.

[0012] These IPS displays can be operated with liquid-crystallinematerials having either positive or negative dielectric anisotropy(Δε≠0). With the materials known hitherto, however, relatively highthreshold voltages and long response times are achieved in IPS displays.In addition, the problem of crystallisation of the liquid-crystal mediumat low temperatures may occur in IPS displays containing materials knownhitherto.

[0013] A further, highly promising type of liquid-crystal display arethe so-called “axially symmetric microdomain” (ASM for short) displays,which are preferably addressed by means of plasma arrays (PA LCDs, from“plasma-addressed liquid-crystal displays”).

[0014] The displays described above can be of the active matrix orpassive matrix (multiplex) type. Thus, for example, ECB and VA displayswhich are operated as active matrix or multiplex displays have beendescribed, whereas CSH displays are usually operated as multiplexdisplays.

[0015] Matrix liquid-crystal displays of this type are known. Non-linearelements which can be used for individual switching of the individualpixels are, for example, active elements (i.e. transistors). The term“active matrix” is then used, where a distinction can be made betweentwo types:

[0016] 1. MOS (metal oxide semiconductor) or other diodes on a siliconwafer as substrate.

[0017] 2. Thin-film transistors (TFTs) on a glass plate as substrate.

[0018] The use of single-crystal silicon as substrate material restrictsthe display size, since even modular assembly of various part-displaysresults in problems at the joints.

[0019] In the case of the more promising type 2, which is preferred, theelectro-optical effect used is usually the TN effect. A distinction ismade between two technologies: TFTs comprising compound semiconductors,such as, for example, CdSe, or TFTs based on polycrystalline oramorphous silicon. The latter technology is being worked on intensivelyworldwide.

[0020] The TFT matrix is applied to the inside of one glass plate of thedisplay, while the other glass plate carries the transparentcounterelectrode on its inside. Compared with the size of the pixelelectrode, the TFT is very small and has virtually no adverse effect onthe image. This technology can also be extended to fully colour-capabledisplays, in which a mosaic of red, green and blue filters is generallyarranged in such a way that a filter element is opposite each switchablepixel. TFT are usually lit from the back.

[0021] The term MLC displays here covers any matrix display withintegrated non-linear elements, i.e., besides the active matrix, alsodisplays with passive elements, such as varistors or diodes(MIM=metal-insulator-metal).

[0022] MLC displays of this type are particularly suitable for TVapplications (for example pocket TVs) or for high-information displaysfor computer applications (laptops) and in automobile or aircraftconstruction. Besides problems regarding the angle dependence of thecontrast and the response times, difficulties also arise in MLC displaysdue to insufficiently high specific resistance of the liquid-crystalmixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E.,SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay84, September 1984: A 210-288 Matrix LCD Controlled by Double StageDiode Rings, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84,September 1984: Design of Thin Film Transistors for Matrix Addressing ofTelevision Liquid Crystal Displays, p. 145 ff, Paris]. With decreasingresistance, the contrast of an MLC display deteriorates, and the problemof after-image elimination may occur. Since the specific resistance ofthe liquid-crystal mixture generally drops over the life of an MLCdisplay owing to interaction with the interior surfaces of the display,a high (initial) resistance is very important for displays that have tohave acceptable resistance values over a long operating period.

[0023] It is furthermore important that the specific resistance exhibitsthe smallest possible decrease with increasing temperature and afterheating and/or UV exposure. The low-temperature properties of themixtures from the prior art are also particularly disadvantageous. It isdemanded that no crystallisation and/or smectic phases occur, even atlow temperatures, and the temperature dependence of the viscosity is aslow as possible. The MLC displays from the prior art thus do not meettoday's requirements.

[0024] Industrial use of the effects described above in electro-opticaldisplay elements requires LC phases which have to meet a multiplicity ofrequirements. Particularly important here are the chemical resistance tomoisture, air and physical influences, such as heat, radiation in theinfrared, visible and ultraviolet region, as well as direct andalternating electric fields.

[0025] LC phases that can be used in industry are furthermore requiredto have a liquid-crystalline mesophase in a suitable temperature rangeand low viscosity.

[0026] None of the series of compounds having a liquid-crystallinemesophase that have been disclosed hitherto includes an individualcompound which meets all these requirements. In general, therefore,mixtures of from 2 to 25, preferably from 3 to 18, compounds areprepared in order to obtain substances that can be used as LC phases.However, it has not been possible to prepare optimum phases easily inthis way, since liquid-crystal materials of significantly negativedielectric anisotropy were hitherto not available to an adequate extent.

[0027] EP 0 474 062 discloses MLC displays based on the ECB effect. TheLC mixtures described therein are based on 2.3-difluorophenylderivatives which contain an ester, ether or ethyl bridge, but have lowvalues for the voltage holding ratio (HR) after exposure to UV. They aretherefore of low suitability for use in the displays described above.

[0028] There thus continues to be a great demand for MLC displays, inparticular of the ECB, VA, CSH, IPS, ASM and PALC types, having veryhigh specific resistance at the same time as a large working-temperaturerange, short response times even at low temperatures, and low thresholdvoltage which facilitate a multiplicity of grey shades, high contrastand broad viewing angles and which do not exhibit the disadvantagesdescribed above, or only do so to a small extent.

[0029] The invention had the object of providing MLC displays which donot have the disadvantages indicated above or only do so to a smallextent, and preferably at the same time have very high specificresistance values and low threshold voltages.

[0030] It has now been found that this object can be achieved if mediaaccording to the invention are used in LC displays.

[0031] The invention thus relates to a liquid-crystalline medium,characterised in that it comprises one or more compounds of the formulaI

[0032] and one or more compounds of the formula II

[0033] in which

[0034] R¹ is H or alkyl having from 1 to 5 carbon atoms,

[0035] R² is alkoxy having from 1 to 12 carbon atoms,

[0036] R³ is alkenyl having from 2 to 7 carbon atoms,

[0037] R⁴ is alkyl having from 1 to 12 carbon atoms, in which, inaddition, one or two non-adjacent CH₂ groups may be replaced by —O—,—CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are not linkeddirectly to one another, and

[0038] c is 0 or 1.

[0039] The invention furthermore relates to a liquid-crystalline mediumbased on a mixture of polar compounds of negative dielectric anisotropy,characterised in that it comprises one or more compounds of the formulaI and one or more compounds of the formula II.

[0040] The invention furthermore relates to an electro-optical displayhaving active-matrix addressing, in particular a display based on theDAP, ECB, VA, CSH, IPS, ASM or PALC effect, characterised in that itcontains, as dielectric, a liquid-crystalline medium according to Claim1.

[0041] In the compounds of the formula I, R¹ is preferably H orstraight-chain alkyl having from 1 to 4 carbon atoms, in particular H,methyl, ethyl or n-propyl, very particularly preferably H or methyl. R²is preferably straight-chain alkoxy having from 1 to 6 carbon atoms, inparticular methoxy, ethoxy, n-propoxy or n-butoxy.

[0042] The compounds of the formula II are preferably selected from thefollowing formulae:

[0043] in which R^(3a) and R^(4a) are each, independently of oneanother, H, methyl, ethyl or n-propyl, and alkyl is C₁₋₆-alkyl.

[0044] Particular preference is given to compounds of the formulae IIa,IId, IIe and IIg, in particular those of the formulae IIe and IIg inwhich R^(3a) is H or methyl.

[0045] The media according to the invention exhibit very high HR values,low threshold voltages and very good low-temperature stabilities at thesame time as high clearing points. In particular, they exhibitsignificantly reduced rotational viscosity compared with the media fromthe prior art.

[0046] Some preferred embodiments are mentioned below:

[0047] a) Medium which additionally comprises one or more compounds ofthe formula III:

[0048] in which

[0049] R⁵ and R⁶ are alkyl having from 1 to 12 carbon atoms, in which,in addition, one or two non-adjacent CH₂ groups may be replaced by —O—,—CH═CH—, —CO—, —OCO— or —COO—,

[0050] a is 0 or 1.

[0051] b) Medium which additionally comprises one or more compounds ofthe formula IV:

[0052] in which

[0053] R⁵ and R⁶, independently of one another, are as defined in theformula III,

[0054] c) Medium in which the compounds of the formula III are selectedfrom the following formulae:

[0055] in which alkyl is C₁₋₆-alkyl, and R^(5a) is H, methyl, ethyl orn-propyl, in particular H or methyl. Particular preference is given tocompounds of the formulae IIIa, IIIb, IIIc, IIId and IIIf.

[0056] d) Medium in which the compounds of the formula IV are selectedfrom the following formulae:

[0057] in which alkyl is C₁₋₆-alkyl, R is C₁₋₆-alkyl or -alkoxy, and Lis H or F.

[0058] e) Medium which additionally comprises one or more compoundsselected from the formulae Va to Vd:

[0059] in which alkyl is C₁₋₆-alkyl, L is H or F, and X is F or Cl.Particular preference is given to compounds of the formula Va in which Xis F.

[0060] f) Medium which additionally comprises one or more compoundsselected from the formulae VIa and VIb:

[0061] in which R⁵ and R⁶ are as defined in the formula III, and L is Hor F. R⁵ and R⁶ in these compounds are particularly preferablyC₁₋₆-alkyl or -alkoxy.

[0062] g) Medium which additionally comprises one or more compoundsselected from the following formulae:

[0063] in which R⁵ and alkyl are as defined above, and d is 0 or 1. R⁵in these compounds is particularly preferably C₁₋₆-alkyl or -alkoxy, andd is preferably 1. Particular preference is given to compounds of theformulae VIIc, IXb and Xb.

[0064] h) Medium which additionally comprises one or more compounds ofthe formula XII:

[0065] in which R⁵ and R⁶ are as defined in the formula III and arepreferably alkyl having from 1 to 8 carbon atoms.

[0066] i) Medium which additionally comprises one or more compounds ofthe formula XIII:

[0067] in which R⁵ and R⁶ are as defined in the formula III and arepreferably alkyl having from 1 to 8 carbon atoms.

[0068] k) Medium which additionally comprises one or more compoundsselected from the following formulae:

[0069] in which R⁵, R^(5a) and alkyl are as defined above. R⁵ in thesecompounds is particularly preferably C₁₋₆-alkyl or -alkoxy.

[0070] l) Medium which comprises from 1 to 4, preferably 1 or 2,compounds of the formula I and from 1 to 6, preferably 1, 2, 3 or 4,compounds of the formula II.

[0071] m) Medium which essentially consists of from 1 to 4 compounds ofthe formula I, from 1 to 6 compounds of the formula II, from 1 to 10compounds of the formula III and from 1 to five compounds of the formulaIV.

[0072] n) Medium in which the proportion of compounds of the formula Iin the mixture as a whole is from 5 to 35%, preferably from 9 to 25%.

[0073] n) Medium in which the proportion of compounds of the formula IIin the mixture as a whole is from 5 to 50%, preferably from 10 to 36%.

[0074] o) Medium which essentially consists of

[0075] 5-35% of one or more compounds of the formula I,

[0076] 5-50% of one or more compounds of the formula II,

[0077] 25-70% of one or more compounds of the formula II, and

[0078] 2-25% of one or more compounds of the formula IV.

[0079] The liquid-crystal mixture preferably has a nematic phase rangeof at least 80 K, particularly preferably of at least 100 K, and arotational viscosity of not more than 290 mPa·s, preferably not morethan 250 mPa·s.

[0080] The liquid-crystal mixture according to the invention has adielectric anisotropy Δε of from about −0.5 to −7.5, in particular fromabout −2.8 to −5.5, at 20° C. and 1 kHz.

[0081] The birefringence Δn in the liquid-crystal mixture is generallybelow 0.15, in particular between 0.06 and 0.14, particularly preferablybetween 0.07 and 0.12. The dielectric constant Δ_(∥)is generally greaterthan or equal to 3, preferably from 3 to 5.

[0082] The dielectrics may also comprise further additives known to theperson skilled in the art and described in the literature. For example,0-15% by weight of pleochroic dyes may be added, furthermore conductivesalts, preferably ethyldimethyidodecylammonium 4-hexyloxybenzoate,tetrabutylammonium tetraphenylboranate or complex salts of crown ethers(cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258(1973)) may be added in order to improve the conductivity, or substancesmay be added in order to modify the dielectric anisotropy, the viscosityand/or the alignment of the nematic phases. Substances of this type aredescribed, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38281, 24 50 088, 26 37 430 and 28 53 728.

[0083] The individual components of the formulae I, II, III and IV ofthe liquid-crystal mixtures according to the invention are either knownor their methods of preparation can easily be derived from the prior artby the person skilled in the relevant art since they are based onstandard methods described in the literature.

[0084] Corresponding compounds of the formulae I and III are described,for example, in EP 0 364 538.

[0085] Corresponding compounds of the formula II are described, forexample, in EP 0 122 389, DE 26 36 684 and DE 33 21 373.

[0086] The term “alkenyl” in formulae II to IV includes straight-chainand branched alkenyl having up to 12, preferably having from 2 to 7,carbon atoms. Straight-chain alkenyl groups are preferred. Furtherpreferred are C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl,C₆-C₇-5-alkenyl and C₇-6-alkenyl, in particular C₂-C₇-1E-alkenyl,C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl.

[0087] Of these groups, particular preference is given to vinyl,1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl,3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl,4E-hexenyl, 4Z-heptenyl, 5-hexenyl and 6-heptenyl. Alkenyl groups havingup to 5 carbon atoms are particularly preferred.

[0088] The nematic liquid-crystal mixtures in the displays according tothe invention generally comprise two components A and B, whichthemselves consist of one or more individual compounds.

[0089] Component A has significantly negative dielectric anisotropy andgives the nematic phase a dielectric anisotropy of ≦−0.3. It preferablycomprises compounds of the formulae I and III.

[0090] The proportion of component A is preferably between 45 and 100%by weight, in particular between 60 and 90% by weight.

[0091] For component A, one or more individual compounds which have avalue of Δε of ≦−0.8 are preferably selected. This value must be morenegative the smaller the proportion of component A in the mixture as awhole.

[0092] Component B has pronounced nematogeneity and a rotationalviscosity of not greater than 250 mpa·s.

[0093] Component B is monotropically or enantiotropically nematic, hasno smectic phases and is able to prevent the occurrence of smecticphases down to very low temperatures in liquid-crystal mixtures. Forexample, if various materials of high nematogeneity are added to asmectic liquid-crystal mixture, the nematogeneity of these materials canbe compared through the degree of suppression of smectic phases that isachieved. A multiplicity of suitable materials is known to the personskilled in the art from the literature. Particular preference is givento compounds of the formula II.

[0094] The liquid-crystal mixtures according to the invention preferablycomprise from 4 to 25, in particular from 6 to 18, compounds of theformulae I, II, III and IV.

[0095] Besides the compounds of the formulae I, II, III and IV, otherconstituents may also be present, for example in an amount of up to 45%by weight of the mixture as a whole, but preferably up to a maximum of35% by weight, in particular up to a maximum of 10% by weight.

[0096] The other constituents are preferably selected from neratic ornematogenic substances, in particular known substances, from the classesof the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenylor cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates,phenylcyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes,cyclohexylnaphthalenes, 1.4-biscyclohexylbiphenyls orcyclohexylpyrimidines, phenyl- or cyclohexyldioxanes, optionallyhalogenated stilbenes, benzyl phenyl ethers, tolans and substitutedcinnamic acids.

[0097] The most important compounds which are suitable as constituentsof liquid-crystal mixtures of this type can be characterised by theformula XV

R⁸-L-G-E-R⁹   XV

[0098] in which

[0099] L and E are each a carbocyclic or heterocyclic ring system fromthe group formed by 1.4-disubstituted benzene and cyclohexane rings,4.4′-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexanesystems, 2.5-disubstituted pyrimidine and 1.3-dioxane rings,2.6-disubstituted naphthalene, di- and tetrahydronaphthalene,quinazoline and tetrahydroquinazoline,

[0100] G is —CH═CH— —N(O)═N—

[0101] —CH—CQ- —CH═N(O)—

[0102] —C≡C— —CH₂—CH₂—

[0103] —CO—O— —CH₂—O—

[0104] —CO—S— —CH₂—S—

[0105] —CH═N— —COO-Phe-COO—

[0106] or a C—C single bond,

[0107] Q is halogen, preferably chlorine, or —CN, and

[0108] R⁸ and R⁹ are each alkyl, alkoxy, alkanoyloxy oralkoxycarbonyloxy having up to 18, preferably up to 8, carbon atoms, orone of these radicals is alternatively CN, NC, NO₂, CF₃, F, Cl or Br.

[0109] In most of these compounds, R⁸ and R⁹ are different from oneanother, one of these radicals usually being an alkyl or alkoxy group.Other variants of the proposed substituents are also common. Many suchsubstances or also mixtures thereof are also commercially available. Allthese substances can be prepared by methods known from the literature.

[0110] It goes without saying to the person skilled in the art that theLC mixture according to the invention may also comprise compounds inwhich, for example, H, N, O, Cl and F have been replaced by thecorresponding isotopes.

[0111] The construction of the liquid-crystal displays according to theinvention corresponds to the usual geometry, as described, for example,in EP-A 0 240 379.

[0112] The following examples are intended to explain the inventionwithout limiting it. Above and below, percentages are per cent byweight, unless stated otherwise; all temperatures are indicated indegrees Celsius.

[0113] The following abbreviations are used:

[0114] Furthermore:

[0115] cl.p. denotes the clearing point [° C.]

[0116] Δn denotes the optical anisotropy (birefringence) at 20° C. and589 nm

[0117] Δε denotes the dielectric anisotropy at 20° C. and 1 kHz

[0118] ε_(∥) denotes the dielectric constant parallel to the director at20° C. and 1 kHz

[0119] K₃/K₁ denotes the ratio of the elastic constants K₃ and K₁

[0120] γ₁ denotes the rotational viscosity [mPa·s] (at 20° C., unlessstated otherwise)

[0121] V₀ denotes the capacitive threshold voltage [V]

[0122] LTS denotes the low-temperature stability of the nematic phase(nem.) in test cells (at T in ° C.)

[0123] The display used for measurement of the capacitive thresholdvoltage has two plane-parallel outer plates at a separation of 20 μm andelectrode layers covered with lecithin alignment layers on the insidesof the outer plates which cause a homeotropic edge alignment of theliquid-crystal molecules.

EXAMPLE 1

[0124] A liquid-crystal display containing PCH-304FF 8.00% cl.p. +70.0PCH-504FF 20.00% Δn 0.1023 CY-V-O4 10.00% Δε −4.1 CCP-302FF 7.00% ε_(∥)3.8 BCH-32 7.00% K₃/K₁ 1.03 CCH-35 5.00% γ₁ 137 CC-3-V1 8.00% V₀ 1.90CC-5-V 11.00% LTS nem. > 1000 h (−30) CPY-2-O2 12.00% CPY-3-O2 12.00%

EXAMPLE 2

[0125] A liquid-crystal display containing PCH-304FF 8.00% cl.p. +70.5PCH-504FF 20.00% Δn 0.1025 CY-V-O4 5.00% Δε −4.0 CY-V-O2 5.00% ε_(∥) 3.8CCP-302FF 7.00% K₃/K₁ 1.01 BCH-32 7.00% γ₁ 136 CCH-35 5.00% V₀ 1.90CC-3-V1 8.00% LTS nem. > 1000 h (−40) CC-5-V 11.00% CPY-2-O2 12.00%CPY-3-O2 12.00%

Comparative Example 1

[0126] A liquid-crystal display containing PCH-304FF 19.00% cl.p. +71.0PCH-504FF 20.00% Δn 0.1020 CCP-302FF 6.00% Δε −3.9 BCH-32 7.00% ε_(∥)3.7 CCH-35 5.00% K₃/K₁ 1.02 CC-3-V1 8.00% γ₁ 142 CC-5-V 11.00% V₀ 1.92CPY-2-O2 12.00% CPY-3-O2 12.00%

[0127] has higher rotational viscosity compared with Examples 1 and 2.

EXAMPLE 3

[0128] A liquid-crystal display containing PCH-502FF 6.00% cl.p. +70.0PCH-504FF 14.00% Δn 0.0891 CY-V-O4 7.00% Δε −3.3 CY-V-O2 7.00% ε_(∥) 3.6CCP-302FF 8.00% K₃/K₁ 1.04 CPY-2-O2 9.00% γ₁ 104 CPY-3-O2 8.00% V₀ 2.13CCP-V2-1 8.00% LTS nem. > 1000 h (−40) CCH-35 5.00% CC-3-V1 9.00% CC-5-V19.00%

EXAMPLE 4

[0129] A liquid-crystal display containing PCH-502FF 6.00% cl.p. +70.2PCH-504FF 10.00% Δn 0.0906 CY-V-O4 9.00% Δε −3.4 CY-V-O2 9.00% ε_(∥) 3.6CCP-302FF 9.00% K₃/K₁ 1.06 CPY-2-O2 8.00% γ₁ 104 CPY-3-O2 9.00% V₀ 2.10CCP-V2-1 8.00% LTS nem. > 1000 h (−40) CCH-35 5.00% CC-3-V1 9.00% CC-5-V18.00%

Comparative Example 2

[0130] A liquid-crystal display containing PCH-304FF 16.00% cl.p. +71.0PCH-504FF 14.00% Δn 0.0822 CCP-302FF 12.00% Δε −3.8 CCP-502FF 11.00%ε_(∥) 3.6 CCP-21FF 9.00% K₃/K₁ 1.08 CCP-31FF 8.00% γ₁ 135 CCH-34 8.00%V₀ 2.08 CCH-35 9.00% LTS nem. > 1000 h (−20) PCH-53 7.00% PCH-301 6.00%

[0131] has higher rotational viscosity and lower Δn and worselow-temperature stability compared with Examples 3 and 4.

EXAMPLE 5

[0132] A liquid-crystal display containing PCH-304FF 7.00% cl.p. +75.0PCH-502FF 10.00% Δn 0.1201 CY-1V-O2 10.00% Δε −3.7 CY-1V-O4 9.00% γ₁ 148PGIGI-3-F 3.00% BCH-32 9.00% CCP-V-1 8.00% CC-3-V1 11.00% PCH-53 7.00%CPY-2-O2 13.00% CPY-3-O2 13.00%

Comparative Example 3

[0133] A liquid-crystal display containing PCH-304FF 20.00% cl.p. +74.5PCH-502FF 8.00% Δn 0.1204 PCH-504FF 8.00% Δε −3.7 PGIGI-3-F 8.00% γ₁ 160BCH-32 8.00% CCP-V-1 7.00% CC-3-V1 8.00% CC-5-V 7.00% CPY-2-O2 14.00%CPY-3-O2 12.00%

[0134] has higher rotational viscosity compared with Example 5.

EXAMPLE 6

[0135] A liquid-crystal display containing PCH-304FF 6.00% cl.p. +72.0PCH-502FF 8.00% Δn 0.0959 PCH-504FF 8.00% Δε −3.4 CY-1V-O4 10.00% γ₁ 109CCQY-3-O2 6.00% CCQY-5-O2 6.00% CPY-V-O2 9.00% CPY-V-O4 9.00% BCH-324.00% CC-3-V1 10.00% CCH-35 12.00% CC-3-V 8.00% PCH-302 4.00%

Comparative Example 4

[0136] A liquid-crystal display containing PCH-304FF 16.00% cl.p. +70.5PCH-502FF 8.00% Δn 0.0954 PCH-504FF 12.00% Δε −3.4 CPY-3-O2 8.00% γ₁ 122CCQY-3-O2 5.00% CCQY-5-O2 5.00% CPY-2-O2 9.00% BCH-32 8.00% CC-3-V18.00% CCH-35 5.00% CC-5-V 16.00%

[0137] has higher rotational viscosity compared with Example 6.

EXAMPLE 7

[0138] A liquid-crystal display containing PCH-502FF 9.00% cl.p. +83.0PCH-504FF 14.00% Δn 0.1031 CY-V-O4 10.00% Δε −4.8 CCP-302FF 14.00% ε_(∥)3.7 CCP-31FF 8.00% K₃/K₁ 1.10 CC-3-2V 8.00% γ₁ 178 CC-3-V1 8.00% V₀ 1.93CCH-35 5.00% LTS nem. > 1000 h (−40) CPY-2-O2 12.00% CPY-3-O2 12.00%

Comparative Example 5

[0139] A liquid-crystal display containing PCH-304FF 8.00% cl.p. +83.5PCH-502FF 8.00% Δn 0.1022 PCH-504FF 18.00% Δε −4.9 CCP-302FF 14.00%ε_(∥) 3.8 CCP-31FF 7.00% K₃/K₁ 1.05 CC-5-V 8.00% γ₁ 189 CC-3-V1 8.00% V₀1.93 CCH-35 5.00% LTS nem. > 1000 h (−40) CPY-2-O2 12.00% CPY-3-O212.00%

[0140] has higher rotational viscosity compared with Example 7.

EXAMPLE 8

[0141] A liquid-crystal display containing PCH-304FF 10.00% cl.p. +106.0PCH-504FF 3.00% Δn 0.1043 CY-1V-O4 9.00% Δε −4.7 CY-1V-O2 9.00% γ₁ 287CCP-202FF 5.00% CCP-302FF 9.00% CCP-502FF 9.00% CCP-21FF 7.00% CCP-31FF8.00% CCY-2O-1 4.00% CCY-4O-1 7.00% BCH-32 3.00% CCP-V-1 10.00% CBC-33F4.00% CC-3-V1 3.00%

Comparative Example 6

[0142] A liquid-crystal display containing PCH-304FF 10.00% cl.p. +106.0PCH-502FF 7.00% Δn 0.1007 PCH-504FF 10.00% Δε −4.7 CCP-202FF 6.00% γ₁315 CCP-302FF 9.00% CCP-502FF 9.00% CCP-21FF 7.00% CCP-31FF 10.00%CCY-2O-1 9.00% CCY-4O-1 6.00% BCH-32 3.00% CCP-V-1 8.00% CBC-33F 4.00%CC-3-V1 3.00%

[0143] has higher rotational viscosity compared with Example 8.

EXAMPLE 9

[0144] A liquid-crystal display containing PCH-502FF 10.00% cl.p. +77.0PCH-504FF 7.00% Δn 0.1018 CY-1V-O2 7.00% Δε −3.9 CY-1V-O4 7.00% γ₁ 124CCP-302FF 6.00% CCP-31FF 5.00% CC-3-V1 10.00% CC-3-2V 8.00% CC-5-V14.00% CPY-2-O2 12.00% CPY-3-O2 11.00% BCH-32 3.00%

Comparative Example 7

[0145] A liquid-crystal display containing PCH-304FF 12.00% cl.p. +76.5PCH-502FF 7.00% Δn 0.0990 PCH-504FF 13.00% Δε −4.0 CCP-302FF 11.00% γ₁138 CC-3-V1 10.00% CC-5-V 19.00% CPY-2-O2 12.00% CPY-3-O2 12.00% BCH-324.00%

[0146] has higher rotational viscosity compared with Example 9.

EXAMPLE 10

[0147] A liquid-crystal display containing PCH-304FF 5.00% cl.p. +74.5PCH-502FF 5.00% Δn 0.1102 PCH-504FF 6.00% Δε −3.2 CY-1V-O2 10.00% γ₁ 125CY-1V-O4 9.00% BCH-32 9.00% CCP-V-1 10.00% CC-5-V 7.00% PCH-53 6.00%CC-3-V1 11.00% CPY-2-O2 11.00% CPY-3-O2 11.00%

EXAMPLE 11

[0148] A liquid-crystal display containing PCH-502FF 10.00% cl.p. +70.5PCH-504FF 8.00% Δn 0.1096 CY-V-O2 9.00% Δε −3.3 CY-V-O4 9.00% γ₁ 118BCH-32 9.00% CCP-V-1 11.00% CC-5-V 6.00% PCH-53 2.00% CC-3-V1 12.00%CPY-2-O2 12.00% CPY-3-O2 12.00%

Comparative Example 8

[0149] A liquid-crystal display containing PCH-304FF 14.00% cl.p. +70.0PCH-502FF 8.00% Δn 0.1106 PCH-504FF 14.00% Δε −3.3 BCH-32 9.00% γ₁ 135CCP-V-1 7.00% PGIGI-3-F 3.00% CC-5-V 8.00% PCH-53 5.00% CC-3-V1 8.00%CPY-2-O2 12.00% CPY-3-O2 12.00%

[0150] has higher rotational viscosity compared with Examples 10 and 11.

EXAMPLE 12

[0151] A liquid-crystal display containing PCH-502FF 10.00% cl.p. +70.0PCH-504FF 14.00% Δn 0.1015 CY-1V-O2 8.00% Δε −4.2 CY-1V-O4 10.00% γ₁ 172CPY-2-O2 8.00% CPY-3-O2 8.00% CCP-V-1 11.00% CCH-35 4.00% CC-3-V1 10.00%CC-5-V 3.00% CPQIY-3-O4 7.00% CPQIY-5-O4 7.00%

Comparative Example 9

[0152] A liquid-crystal display containing PCH-304FF 17.00% cl.p. +70.5PCH-502FF 9.00% Δn 0.0993 PCH-504FF 14.00% Δε −4.2 CPY-2-O2 7.00% γ1 187CPY-3-O2 7.00% CCP-V-1 12.00% CCH-35 5.00% CC-3-V1 9.00% CPQIY-3-O410.00% CPQIY-5-O4 10.00%

[0153] has higher rotational viscosity compared with Example 12.

1. Liquid-crystalline medium, characterised in that it comprises one ormore compounds of the general formula I

and one or more compounds of the formula II

in which R¹ is H or alkyl having from 1 to 5 carbon atoms, R² is alkoxyhaving from 1 to 12 carbon atoms, R³ is alkenyl having from 2 to 7carbon atoms, R⁴ is alkyl having from 1 to 12 carbon atoms, in which, inaddition, one or two non-adjacent CH₂ groups may be replaced by —O—,—CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are not linkeddirectly to one another, and c is 0 or
 1. 2. Medium according to claim1, characterised in that it additionally comprises one or more compoundsof the formula III

in which R⁵ and R⁶ are alkyl having from 1 to 12 carbon atoms, in which,in addition, one or two non-adjacent CH₂ groups may be replaced by —O—,—CH═CH—, —CO—, —OCO— or —COO—,


3. Medium according to claim 1 or 2, characterised in that itadditionally comprises one or more compounds of the formula IV

in which R⁵ and R⁶, independently of one another, are as defined in theformula III,

b is 0 or
 1. 4. Medium according to at least one of claims 1 to 3,characterised in that it comprises one or more compounds selected fromthe following formulae:

in which alkyl is C₁₋₆-alkyl, and R^(5a) is H, methyl, ethyl orn-propyl, in particular H or methyl.
 5. Medium according to at least oneof claims 1 to 4, characterised in that it comprises one or morecompounds selected from the following formulae:

in which alkyl is C₁₋₆-alkyl, R is C₁₋₆alkyl or -alkoxy, and L is H orF.
 6. Medium according to at least one of claims 1 to 5, characterisedin that it comprises one or more compounds selected from the followingformulae:

in which R⁵ and R⁶ are as defined in claim 2, alkyl is C₁₋₆-alkyl, L isH or F, X is F or Cl, and d is 0 or
 1. 7. Medium according to at leastone of claims 1 to 6, characterised in that it essentially consists offrom 1 to 4 compounds of the formula I, from 1 to 6 compounds of theformula II, from 1 to 10 compounds of the formula III and from 1 to fivecompounds of the formula IV.
 8. Medium according to at least one ofclaims 1 to 7, characterised in that the proportion of compounds of theformula I in the mixture as a whole is from 5 to 35%, preferably from 9to 25%.
 9. Medium according to at least one of claims 1 to 6,characterised in that the proportion of compounds of the formula 11 inthe mixture as a whole is from 5 to 50%, preferably from 10 to 36%. 10.Medium according to at least one of claims 1 to 6, characterised in thatit essentially consists of 5-35% of one or more compounds of the formulaI, 5-50% of one or more compounds of the formula II, 25-70% of one ormore compounds of the formula III, and 2-25% of one or more compounds ofthe formula IV.
 11. Electro-optical display having active-matrixaddressing, characterised in that it contains, as dielectric, aliquid-crystalline medium according to at least one of claims 1 to 10.12. Electro-optical display according to claim 11, characterised in thatit is based on the ECB, VA, DAP, CSH, IPS, ASM or PALC effect.